At this time all the major intravenous set manufacturers make and market intravenous administration sets which allow the addition of a second solution via a second intravenous set which automatically stops the flow of the primary set by the use of a check valve in the primary set when the fluid level of the second solution is higher than the first solution.
At the point where the second solution level is drained to the level of the first solution, the check valve opens and the first solution begins to run but at the same rate as was set for the second solution. This is because both solutions must be regulated by the same flow restriction or control device which must be below the place where the two sets join in order to eliminate the potential of drawing air into the line.
As in the majority of instances, the secondary set rate is higher, flowing faster, than the first (primary or keep open) set rate, this necessitates the nurse or attendant returning and resetting the flow rate after the second solution has run out. Failure to do this can lead to very serious complications or death to critically ill individuals. Adjustable flow control clamps or devices have been used in connectionn with intravenous sets and are assembled onto the usually transparent plastic tubing for controlling the flow rate therethrough. An example of such flow control clamp is shown in U.S. Pat. No. 3,685,787. Such clamp includes a movable element which operatively engages a wall of the tubing for leaving it fully open or progressively reducing its cross sectional area to the point of closing off all flow. Other types of flow control clamps may be used as is well known in the art such as roller clamps, slide clamps, screw clamps and other flow control devices.
Conventional intravenous sets normally utilize a check valve in the primary tubing above the connector site responsive to pressure by which if the secondary solution is maintained at a level above the level of the primary solution, during the flow of the secondary solution into and through the connector site the check valve is effective to cut off all flow of the primary solution.
Heretofore, in the application of a secondary solution by the usual Y-connector site into the primary intravenous set, close attention is required by the nurse or operator so that once the secondary solution has been exhausted the conduit therefor will be closed off to prevent the accidental introduction of air into the primary intravenous set.